This invention relates to a group radio communication system which implements point-to-multipoint communications. More specifically, the present invention relates to independent radio sub-networks each of which implement point-to-multipoint communications within their domains and are coupled together through a group controller to form an overall network for point-to-multipoint communications.
Point-to-multipoint (PTM) refers to a communication circuit in which a single signal goes from one originating group member to many destination or target group members. PTM communication can be implemented by sharing common communication resources among many users. PTM communication has been long practiced in connection with commercial broadcast radio and television, where the origination point remains static and the communication resources are allocated for very long durations. However, the origination point may also shift, as occurs in two-way and dispatch radio.
A PTM communication session may take place for an indefinite period of time on the scale of weeks, months, or years, for several hours, or for a shorter duration. Within a PTM communication session, a point-to-multipoint monolog occurs when one group member is originating information that is being broadcast to the other members of the group. The duration of a monolog is desirably controlled by the group member originating the monolog. When the originator ceases to originate information, the monolog ceases. Desirably, that group member or other group members may originate another monolog thereafter within the same communication session; however, nothing requires any group member to originate a monolog at any given instant. For voice communications, a monolog typically lasts only a few seconds, although nothing requires any particular duration.
One problem with existing group radio communication systems that provide PTM communication sessions is their frequent failure to use existing communication infrastructures efficiently, resulting in increased costs, limited coverage areas, and limited ability to extend the group to cover additional members. Existing communication infrastructures, and particularly cellular radio infrastructures, are typically configured to optimize the delivery of point-to-point (PTP), as opposed to PTM, communications. However, infrastructure costs are typically low on a per-user basis because they are shared by a vast number of users, and the coverage area may be up to world wide.
Another problem is that conventional group radio systems are often incompatible with one another due to system incompatibilities or remote locations. Thus, one group system, such as a city police department, may not be able to participate in a common group communication session with another group system, such as a federal agency, even when located in the same area. Due to limited coverage areas, even members of compatible systems, such as police departments in different towns, may not be able to participate in a common group communication session